Lead-acid batteries as used in automobiles, lighting, and the like, are produced in a top terminal configuration, as well as a side terminal configuration. With a top terminal design, tapered terminals project upwardly from the top wall of the case and receive cable clamps.
In a side terminal design, the terminals extend outwardly of the side wall and in a typical design, each terminal includes a lead bushing which is mounted within a recess in the side wall of the case. The inner end of the bushing projects through an opening in the side wall of the case and is welded to a conductor strap which is connected to the electrode plates.
In the typical side terminal construction, a stainless steel nut is mounted within a recess in the outer surface of the lead bushing and the cable clamping ring is connected to the bushing by a bolt, which is threaded within the stainless steel nut.
A side terminal battery has certain advantages over a top terminal configuration. The side terminal design provides a lower profile for the battery and as the terminals are located along the side wall, they are removed from the vents in the top wall of the case, through which hydrogen and oxygen can be vented. In addition, with a side wall terminal design, electrical conductive contaminants cannot collect on the side wall and bridge the terminals, as can occur with a top terminal construction.
However, a problem has arisen with side terminal designs, in that if the original bolt is lost or misplaced, the user will invariably substitute a replacement bolt, which has a longer length than required. As the longer bolt is threaded into the nut to clamp the cable to the bushing, the inner end of the longer bolt will bottom out and as torque is continued to be applied to the bolt, the bottom of the malleable lead bushing will deform and in some instances the deformation of the bushing will break the weld between the bushing and the strap. This can result in arcing if a heavy load is encountered, which results in an ignition source and rapid combustion of the hydrogen gas within the battery.